Rhodamine-based fluorescent probe for sequential detection of Al³⁺ ions and adenosine monophosphate in water

Organic nanoparticles (N1) were prepared by dispersing thiophene-conjugated rhodamine derivative 1 in a buffer solution (10 mM TRIS, pH 7.4, containing 1% DMSO, v/v). N1 selectively recognized Al³⁺ ions through the "OFF-ON" switching mechanism of the spirolactam ring in rhodamine. The resulting N1·Al³⁺ complex recognized the biologically important molecule adenosine monophosphate (AMP) through a cation displacement process with a detection limit of 2 nM. N1 was capable of determining the concentration of Al³⁺ ions in environmental and biological samples. Portable test strips of N1 were prepared for the recognition of Al³⁺ ions and AMP for practical uses. Furthermore, it was demonstrated that the N1·Al³⁺ complex facilitated real-time monitoring of AMP concentration in the hydrolysis of ATP and ADP.